Gas turbine engines include a fan inlet that directs air to a compressor for compressing air. Typically, part of the compressed air is mixed with fuel in a combustor and ignited. The exhaust enters a turbine assembly, which produces power. Exhaust leaving the combustor reaches temperatures in excess of 1000 degrees Celsius. Thus, turbine assemblies are exposed to the high temperatures. Turbine assemblies are constructed from materials that can withstand such temperatures. In addition, turbine assemblies often contain cooling systems that prolong the usable life of the components, including rotating blades and stationary vanes. The cooling systems reduce the likelihood of oxidation due to exposure to excessive temperatures. The cooling systems are supplied with cooling fluid from part of the compressed air stream and air that enters the engine at the fan and bypasses the combustor.
The stationary vanes of the turbine assembly may be cooled by directing a cooling fluid through a series of internal passages contained within the airfoil of the vane. The internal passages create a cooling circuit. The cooling circuit of a vane will receive the cooling fluid from the cooling system to maintain the whole of the vane at a relatively uniform temperature.
Airflow through the vane cooling circuit is typically determined by the vane design, and is typically the same for all vanes in a single stage of the engine. The vane cooling circuit may include several internal cavities. It is often desirable to adjust and tune the cooling flow through the vane cooling circuit.
To adjust the flow, current technologies adhere a thin sheet metal plate that has one or more holes over one of the internal cavity inlets at the outer diameter of the vane. The metering plate placed at the internal cavity inlet does decrease the flow through the cavity, but it also causes the pressure of the cavity to drop. The contraction and expansion of air as it is forced through the metering plate magnifies the pressure drop, and thus efficacy of the cooling air. Another common way to adjust flow through in the vane is to use an inner diameter rib termination adjacent the bottom of the cavity to meter the flow of the cooling fluid. However, these inner diameter features are designed into the vane casting, and do not allow for post-casting adjustments to the fluid flow. While advances have been made in the cooling circuits contained within vane airfoils, a need still exists for a vane which has tunable cooling efficiency.